I have completed the power test of IMSAI 8080 #2 with Thinkertoy wunderbuss mother/backplane board, Dan Roganti sent me useful testing info, it helps my confidence to know for sure that I am doing it correctly.

The original owner may have had the yellow and orange crossed (-16 and +16). That would explain the blow outs. I was careful to preserve the order that the wires were originally set so that when I removed the board I could put it back the way it was:

I have since then swapped the yellow and orange wires so that next time I will not assume the previous owner of a computer has it wired correctly!

How this could have happened, here's my guess:

1. The +16v capacitor unformed (or deformed or whatever you call it)
2. The orig owner thought, hmmm, maybe the +16 and -16 are backwards, let's try the other way...
3. POP
4. Then I buy it for $300 from a guy down the road
5. I replace the 4 tantalum capacitors on c15-c18
6. I turn on the power
7. The MC78M12CT (on the schematic it's IC4) starts to smoke (but the replaced c15-c18 are OK
8. Today - I tested the power (I now will always do this FIRST!....I am learning) with results below.

Progress with the IMSAI 8080 that I have with the Thinkertoy Wunderbus backplane.

What was once a box of parts is now a semi-working computer.

Thanks to Mike and Dan for their help.

1. While probing the power supply board Dan sparked a diode, and somehow that woke it up, now functioning. There may have been something touching it.
2. Replaced a 12V Regulator on the backplane board
3. Re-assembled front panel.
4. Put in a new connector for the on-off switch wire from the front panel to the power supply board.
5. Replaced the 8080 processor chip on the CPU card.

Now the system works, but after a few minutes the front panel starts to flicker and is no longer reliably responsive.

Next:
1. Test chips on the front panel board, see if there is a short someplace, etc.